The present invention relates to a knee-joint endoprosthesis which enables at least one of the condyles of the thigh-bone or femur (the sliding parts of the femur) to be replaced by a wear-resistant member embodying condylar replacement surface means, in the form of a sliding or rolling pad for anchoring in the femoral bone to make good a damaged part of the femur, and which enables one or both of the associated plateaus on the shin-bone or tibia to be replaced, in accordance with the depth of the wear, by a replacement part made of wear-resistant plastics material. It is to be understood that the word "pad" as herein used has approximately the same or a similar connotation to the word "pad" when used to define the surface of an animal's paw that comes into contact with the ground.
Hitherto, known knee-joint endoprostheses have been so designed that damaged portions of the condyles of the thigh-bone are replaced by sliding pads of wear-resistant material which are anchored in cavities made in the condyles by means of spigots, ribs or the like. The lateral boundary faces of each pad in its extent from front to rear are parallel and in the longitudinal and transverse directions each pad is curved, two parallel pads being connected rigidly together by a yoke in the upper frontal area in cases where both femoral condyles are damaged. This means that the upper frontal portion of the pad does not rest flat against what remains of the natural femoral condyles and results in ridges which the knee cap has to cross when the joint is moved, which is painful. In addition, the parallel position of the pads hampers rotary movement of the shin-bone relative to the thigh bone. Furthermore, in known prostheses the tibial plateaus which replace the similarly worn tibial surfaces are made flat, so that as a result no proper bending and rotary movement of the bones relative to one another is possible as it is in the natural knee-joint.
It is an object of the invention to produce an endoprosthetic member for the femoral condyles and tibial plateaus which conform to the natural parts, in such a way that proper painless movement of the joint is possible with a smooth and unhampered sliding movement of the knee cap.